Waveguide



Aug. 15, 1967 KRANK T L 3,336,544

WAVEGUIDE Filed July 19, 1965 INVENTORS Wolfgang Kronk a Gerhard Schickie MKW ATTO

United States Patent 3,336,544 WAVEGUIDE Wolfgang KrauK and Gerhard Schickle, Backnang, Germany, assignors to Telefuuken Patentverwertungsgesellschaft m.b.H., Ulm (Danube), Germany Filed July 19, 1965, Ser. No. 472,851 Claims priority, application Germany, July 18, 1964, T 26,624; Sept. 19, 1964, T 27,039 8 Claims. (Cl. 333-95) The present invention relates generally to waveguides and, more particularly, to the type which can be wound on a drum, which has a cross-sectional edge which is even or free of abrupt changes of direction, and which serves for the transmission of electromagnetic waves at very high frequencies.

Waveguides with various cross-sectional shapes are already known. For example, the use of waveguides which are square in cross-section is known for the simultaneous transmission of two electromagnetic waves which are polarized perpendicular to one another. These rigid waveguides can only be produced in relatively short lengths and, therefore, the individual lengths have to be joined to one another by flange connections.

For this same purpose, a separate waveguide for each type of polarization to. be transmitted and particularly for feeding antennas, has been proposed. However, this involves a considerable expense.

For mobile radio stations, it is often desirable, if not actually necessary, to construct the mentioned feeders in the form of flexible lines which can be wound on a drum. The corrugated-tube waveguide of elliptical crossse-ction, which has recently become known, represents an appropriate solution. However, transitions to the standardized cross-section are necessary for these wave-guides, so that new fittings have to be developed for this purpose.

With this in mind, it is the object of the invention to provide a new waveguide which can be wound on a drum.

Another object of the invention is to provide a flexible, corrugated waveguide which is welded and has a longitudinal seam and is substantially rectangular in crosssec-tion.

These objects and others ancillary thereto are accomplished in accordance with preferred embodiments of the invent-ion wherein there is provided a waveguide which can be wound on a drum and which has a cross-sectional edge which is free of abrupt changes of direction and is suited for the transmission of electromagnetic waves at very high frequencies. The waveguide is formed by a corrugated metal tube welded with a longitudinal seam, preferably a helically corrugated metal tube, which is substantially rectangular in cross section.

Becaues of the corrugated cross-section, a waveguide constructed in this manner is so flexible that it can be Wound on a cable drum without adversely alfecting the electrical characteristics. Depending on the flexibility required, the sides of the cross-section of the tube are either curved symmetrically outwardly or made as rectilinear as possible, the corners being rounded with a small radius of curvature. If the sides are curved outwardly, the tensile strength is increased at the same time.

The waveguide may be rectangular in cross-section so that a rectangular waveguide is obtained which can be manufactured continuously and wound on a drum. It is also possible to select a square cross-section. This has the advantage that two electromagnetic waves which are polarized perpendicular to one another can be transmitted simultaneously with one feeder line.

The following conditions should be adhered to for the dimensioning of the waveguide:

3,336,544 Patented Aug. 15, 1967 Here, b represents the length of the ridge of a cormgation in the waveguide, and b the length of a corresponding trough of a corrugation. The depth of the corrugation is designated by w and the largest internal axis of the waveguide -by a.

Flexible waveguides of short length (maximum 1 meter) are already known which are constructed in the form of corrugated waveguides. They, are used primarily for installation in a rigid waveguide in order to compensate for variations in length caused by heat, expansion or, in the case of antenna feeders, to compensate for the rotation of the antenna during the adjustment of the direction of the radio field. These waveguides had a ratio of b /b and w/a0.03, and a pitch angle which is less than 3. The invention is based on the recognition of the fact that long waveguides which satisfy the electrical requirements cannot be built with the above-mentioned dimensions.

The waveguide dimensioned according to the invention has satisfactory characteristics from the electrical point of view and at the same time is still so flexible that it can be wound on a drum which is of decisive importance for the transportation of such feeder lines. Flexible waveguides are generally provided with a corrugation running helically. If the present waveguide is likewise helica lly corrugated, then it is advisable to select the corrugation pitch between 3 and 10, a corrugation pitch of 6 being preferred.

The shape of the corrugation may be substantially sinusoidal, but for special applications, it is also possible to provide a trapezoidal corrugation without adversely affecting the characteristics of the waveguide.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a diagrammatic view of a short length of a substantially sinusoidally corrugated waveguide section.

FIGURE 2 is a schematic perspective view of a waveguide which is substantially square in cross-section.

FIGURE 3 is a schematic perspective view of the waveguide shown in FIGURE 2 but with a plastic sheath.

With more particular reference to the drawings, in FIG- URE 1, the length of the ridge of a corrugation is designated by b while the intermediate shorter trough of the corrugation is designated b The depth of the corrugation of the waveguide is designated by w. The ratio between the depth of the corrugation and the largest internal dimension of the waveguide is preferably selected at 0.07 within the given range, while a particularly favorable ratio of [2 to b was found to be 1.12.

FIGURE 2 is a perspective view of a waveguide which is constructed in accordance with the invention and which is substantially square in cross-section, that is to say it is symmetrical with respect to the vertical and horizontal axes A and B. Its sides are curved slightly outwardly and the so-called corners are curved and have a small radius of curvature in order to increase the flexibility.

A waveguide dimensioned according to the invention may be used instead of the rigid rectangular or square waveguides hitherto known. Neither waveguide bend nor twist is necessary with the invention in view of the flexibility and twistability of the waveguide, so that a continuous waveguide is obtained which satisfies all the requirements and does not comprise any flange connections.

In order to prevent the waveguide from being damaged during transportation, it is advisable to cover the whole corrugated-tube waveguide by a Wear-resistant plastic sheath which, at the same time, affords protection against corrosion.

A waveguide constructed in accordance with the present invention is preferably manufactured in such a manner that a round metal tube welded with a longitudinal seam is provided in a continuous operation with the appropriate corrugation, whereupon it is deformed into the required cross-section in a calibrating device, and is then provided with a plastic jacket by means of a plastic spraying device so that the troughs of the corrugations are filled with plastic material.

Apart from the required flexibility, the construction of the waveguide in the form of a corrugated tube welded with a longitudinal seam has the advantage that it can be produced in a continuous operation in any desired length by an appropriate cable-making machine.

The so called corners of the waveguide are rounded with a small radius of curvature. The radius depends on the flexibility required. Usually this radius r is between 0.05 and 0.25 wavelength of the guide.

In FIGURE 3 there is shown the waveguide of FIG- URE 2 which has now a wear-resistant plastic sheath 2 extending into the grooves of the waveguide 1. The plastic sheath gives protection against unwanted damage after laying the waveguide.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. In a waveguide which can be wound on a drum and has a cross-sectional edge which is free of abrupt changes of direction for the transmission of electromagnetic waves at very high frequency, the improvement wherein the waveguide is a corrugated metal tube which is welded with a longitudinal seam, and is substantially rectangular in cross section, the sides of the cross section being curved outwardly symmetrically.

2. In a waveguide which can be wound on a drum and has a cross-sectional edge which is free of abrupt changes of direction for the transmission of electromagnetic waves at very high frequency, the improvement wherein the waveguide is a corrugated metal tube which is Welded with a longitudinal seam, and is substantially rectangular in cross section, the sides of the cross section being curved outwardly symmetrically, and the wave-guide having the following relationships:

12 represents the length of a ridge of the corrugation; b represents the length of a trough of the corrugation; w represents the depth of the corrugation; and

a represents the largest internal axis of the waveguide.

3. A waveguide as defined in claim 2 wherein the waveguide is helically corrugated.

4. A waveguide as defined in claim 2 wherein b b is 1.12 and w/a is 0.07.

5. A waveguide as defined in claim 2 wherein the corrugation has a pitch which is between 3 and 10.

6. A waveguide as defined in claim 5 wherein the corrugation pitch is 6.

7. A waveguide as defined in claim 2 comprising a wearresistant plastic sheath surrounding the waveguide.

8. A waveguide as defined in claim 7 wherein plastic fills the troughs in the corrugations.

References Cited UNITED STATES PATENTS Van Nostrand Company, Inc., 1953, p. 292.

HERMAN KARL SAALBACH, Primary Examiner.

L. ALLAHUT, Assistant Examiner. 

1. IN A WAVEGUIDE WHICH CAN BE WOUND ON A DRUM AND HAS A CROSS-SECTIONAL EDGE WHICH IS FREE OF ABRUPT CHANGES OF DIRECTION FOR THE TRANSMISSION OF ELECTROMAGNETIC WAVES AT VERY HIGH FREQUENCY, THE IMPROVEMENT WHEREIN THE WAVEGUIDE IS A CORRUGATED METAL TUBE WHICH IS WELDED WITH A LONGITUDINAL SEAM, AND SUBSTANTIALLY RECTANGULAR IN CROSS SECTION, THE SIDES OF THE CROSS SECTION BEING CURVED OUTWARDLY SYMMETRICALLY. 